The present invention relates to a negative pressure booster equipment to be used for brake booster, and more particularly, to a negative pressure booster equipment, in which a retainer to support the spring of control valve is provided on an input shaft.
For the vehicles such as passenger car, negative pressure booster equipment utilizing negative pressure has been conventionally used for the brake booster. A general negative pressure booster equipment is described, for example, in the Japanese Provisional Patent Publication Sho 58-202146.
In this negative pressure booster equipment, a control valve furnished in the bore of valve body is switched over through a valve plunger when input shaft is operated. Thus, atmospheric air is introduced into variable pressure chamber, and power piston is operated by the pressure difference between variable pressure chamber and constant pressure chamber.
In such negative pressure booster equipment, the input shaft is swinged simultaneously with the axial movement when the brake pedal is depressed. The input shaft and the valve plunger must be connected in order to absorb this swing. For this purpose, the valve plunger and the input shaft are normally connected with each other in such manner that they can be rotated relative to each other, and this is usually done by caulking.
In the control valve, springs are furnished to fix the valve disc on valve body or to apply force on the valve disc toward the direction of valve seat. Further, a retainer is engaged on the input shaft in order to support these springs.
In such negative pressure booster equipment, however, the valve plunger and the input shaft cannot be easily separated because these are connected by caulking connection, and the valve plunger cannot be removed easily from the valve body. Also, the retainer supporting the springs of control valve cannot be removed from the atmospheric air inlet of the valve body. Accordingly, it is very difficult to remove only the valve disc of the control valve. When the valve disc, usually made of rubber easily deteriorated, is to be replaced, for instance, the subassembly incorporating valve plunger, input shaft and control valve on valve body had to be replaced in the past. This means the replacement of the components, which need not be replaced yet.
In the conventional general negative pressure booster equipment, caulking process is required because valve plunger and input shaft are connected by caulking. This resulted in the higher number of fabrication processes and has hindered the automation of the assembling process.
Further, the axial length of the valve plunger guide must be relatively long because valve plunger must be guided in relation to the valve body, and this means longer overall length of the equipment.